I recently met a musician who claims he can quite easily hear the difference between 44.1KHz and 96KHz.

This shocked me a little because I'd always been told that the human ear cannot hear any higher quality than CD (44.1KHz) quality.

So... was this guy just lying (or fooled by his senses), or was I being lied to when I was told the human ear cannot hear any higher quality than CD?

Hi,

this is a 2Khz (stereo) square wave, represented in 16/44.1 PCM

A square wave is actually composed of a sine-wave fundamental (of 2KHz in this case) with an infinite number of it's odd order harmonics folded back into it (3rd, 5th, 7th etc). In fact a'perfect' squarewave doesn't exist, it would have an infintely short rise and decay for each cycle, requiring an infinite number of harmonics, but the more (higher-frequency) of those odd-orders you add, the closer you get to one. This is how the 'edges' needed for digital data transmission are created on such things as analogue phone lines.

This waveform obviously doesn't exist in 'nature', there's no way of producing it acoustically, transmitting it through the air and capturing it with a microphone, it has to be synthesized.

So, this sythesized 2KHz sqaurewave actually has harmonic components extending to 100's of KHz and beyond. Strange but true. You can't 'hear' them, but they're there, they create theis waveform by reinforcing or attenuating the original 2KHz sine.

To actually reproduce this wave 'perfectly' in the analogue domain as the output of a DAC (that is, downstream of it's anti-aliasing filter) is as 'impossible' as the waveform itself is. Filter ringing and phase-shifting between frequencies will produce various effects such as rippling which can be seen graphically if the output is re-captured digitally or monitored in real-time on an oscilloscope.

Now as it happens almost *all* musical instruments produce sound swith harmonic components extending to 40KHz, 50KHz and beyond. Some, such as muted brass produce very substantial pressure levels indeed at these frequencies.

Can we hear them, or sense them in any way? Doubtful (even if you go with the putative non-aural mechanisms some suggest).

BUT they are nonetheless intrinsic to the waveform which results when they are captured - it is *irrelevent* that we cannot 'hear' them, or that the recording hardware or digital protocol is 'band-limited'.

On playback of a recording, the same digital-filtering effects which can be seen graphically in the output of the simple, mathematical square-wave will affect the ultrasonic components of musical instruments and *will* at the very least have an effect on timbre, from innocuous to possibly ear-shredding.

Please don't anybody tell me they *havn't* at some heard point heard a recording of violin or trumpet playing on a CD-based system that didn't make them want to clap their hands over their ears!

I'm not at all surprised to hear that a musician says he/she can hear their instrument reproduced more faithfully with higher sampling rate PCM.

Higher sampling rate = much more benign filtering and more realistic music.

On playback of a recording, the same digital-filtering effects which can be seen graphically in the output of the simple, mathematical square-wave will affect the ultrasonic components of musical instruments and *will* at the very least have an effect on timbre, from innocuous to possibly ear-shredding.

Please don't anybody tell me they *havn't* at some heard point heard a recording of violin or trumpet playing on a CD-based system that didn't make them want to clap their hands over their ears!

R.

>>edits - yptos as usual.

Again, I don't think that filtering artifacts are relevant. The issues only happen with bugged filtering. Recent equipment shouldn't cause audible artifacts. Concerning the bad violin or trumpet, see the other discussion.